when \(j\)  and \(k\)  are far apart in the MBL regime.
In Eq. (REF ) \(\zeta \)  defines a lengthscale over which the corresponding LIOM operators are localized. This lengthscale is related to the spatial correlation length of the eigenstate amplitudes on the Fock-space [1]}, [2]} and expects to diverge at the critical point.
